-32- 
Thus, 
x = b 
p £ f 
(81) 
0. 4 5/-L.Z 
Equation 8l is the "basic equation for determining the Maximum Bridging 
Distance for a combination of fXp ,f-L 0 , f , B and Z. For the 
sake of convenience, the following two equations are derived from 
equation 8l; 
m 
bd (feet) = 0.4 3 B 
jU, f S 
¡JUoZ 
m bd (meters) = 0.047B 
In equations 82 and 83, 
/X f S 
(82) 
(83) 
jLLo Z 
jUL is the tolerated mean square error in planimetry measured on the 
publication scale of the map (in inches or millimeters)^ 
^f o is the accuracy (mean square error) of measurement of parallax in 
the stereomachine in the image plane (in inches or millimeters)^ 
f is the principal distance of the camera used (in inches or milli 
meters )> 
S is the map scale number, 
Bis the average length of the aerial base (in feet or meters)^ 
Z is the average flight height above ground (in feet or meters). 
The same line of thinking is used to determine > using 
equations 50 thru 53> 56 and 57 thru 68. Dropping the terms of 
negligible effect (the terms involving in this case), we get: 
f1.B (! - £f * * <£>*. z 2 < \ -||> 2 ). 
f B 
2 + 
(84) 
/4 H = ^f-X 2 * ~ 2 4 + ~ °* 2 ^3 + 2 | + °* 2 ^j ' (*')